


Distracting a Killer Robot

by FriendshipSuplex



Category: Undertale (Video Game)
Genre: Apology Sex, Gunplay, Light BDSM, Mildly Dubious Consent, Minor Violence, Oral Sex, Other, Reader has no defined gender, Reader-Insert, Smut, Temperature Play, Threats of Violence, choose your own sexventure, one day i'll write mtt not being a jerk i swear
Language: English
Status: Completed
Published: 2015-11-19
Updated: 2015-11-26
Packaged: 2018-05-02 10:23:14
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 4
Words: 3,863
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5244761
Author URL: https://archiveofourown.org/users/FriendshipSuplex/pseuds/FriendshipSuplex
Summary: <blockquote class="userstuff">
              <p>Mettaton's NEO form has been accidentally activated, and Alphys needs you to go in and distract him until his battery runs out so he doesn't go on a murderous rampage. </p><p>Easy, right?</p><p>EDIT: By popular demand, added a part two! Complete with two versions for whatever happens to be in your pants at the moment.</p>
            </blockquote>





	1. Chapter 1

It took you less than 15 minutes to get to Alphys's lab after her text: "Come to lab ASAP need help with mtt." You are naturally a little surprised to see her pacing around outside and not dealing with whatever the mysterious "problem" was. Finally noticing you, she rushes over to you in a panic.

"You're here! Thank god! Mettaton's inside and I need you to, uh... I should explain first." She backs up a bit, noticing your confusion, and takes a deep breath. "So, uh, I asked Mettaton to come in for repairs like usual, since he never does it if I don't ask and he ends up breaking something important and then I have to bring all my stuff to come fix him... uh, but, I may have... accidentally... activated his anti-human combat features? And now he's, uh, a little bit violent. It's part of his programming." She grins at you, sheepishly, and you ask her just how exactly she expects you, a human, to help. "Oh! Well! See, his NEO form-- uh, the combat feature-- uses even more power than his EX form does. So I just need you to go in there and... distract him. For a bit. Until he runs out of power?" 

You ask her why she doesn't just let him blow off steam in the lab and wait for him to run out of power on his own. 

"Well... he's probably not going to stay in there much longer." She grimaces. "I locked the doors, but he could blow them open pretty easily if he wanted. Which... he probably will if he gets too bored. Which is where you come in!" She grabs your arm in a manner you're sure is _supposed_ to be reassuring but just ends up kind of awkward. "You're pretty good friends with him, right? You can just go in there and... talk." You decide not to mention you're not so much "good friends" as much as you made out with him backstage after his show a couple times and had maybe one actually conversation with him. She looks down, a little sad. "He's... already mad at me because I tried to turn him off when I realized what I did. S-so... you're the next person I thought of! You can help, right?" You sigh, and tell her you guess you don't have much choice. "You can do it!" She cheers as you make your way toward the door. You reach a hand out to open it when she stops you again. "W-wait! Uh, if things get too... violent... you can call for me. I'll be listening. And I can probably try to help? But try not to antagonize him too much." You tell her you appreciate her help, and head into the lab. 

\--

It's... dark. You reach for the light switch only to realize the lights are already on, but most of them have been... shot out? You are now dearly hoping you don't regret this. You're barely three steps in when you see him.

The robot on the other side of the lab is unmistakably Mettaton. His chassis is still pink and black, although more... pointy than you're used to. He's facing away from you, but it looks like the side of his face is covered somehow. His right hand seems to have been replaced with an arm cannon, which explains the destroyed lights. You take a particularly loud step (damn these shoes) and he snaps his head to look at you. 

Before you realize it, he's nearly on top of you, and he grabs the front of your shirt to lift you up. "What are _you_ doing here, human?" He growls, and you have never been this inappropriately turned on in your life. This is definitely not the Mettaton you're used to. You stumble out an excuse about wanting to visit him, deciding not to mention Alphys's request. He narrows his eyes at you. "Is that so?" His voice is dripping with disdain as he slowly brings his cannon arm to point at your face.

"I think you're a liar, and I think Alphys sent you to disable me." 

You were wrong. _This_ is the most inappropriately turned on you've ever been. You can feel your cheeks flush red and oh god, he's going to notice. You squirm in his grip, not even trying to defend your actions at this point, but you freeze when he presses the gun to the side of your head. You can't help it: you let out the tiniest grunt-- not even a real moan, you're not _that_ depraved, thank god, but he still takes notice. He pushes the gun against you harder, forcing you to turn your head, and you take the opportunity to look anywhere but at him. Not getting aroused by a murderbot today, you lie to yourself, as you feel your heart pounding in your chest. 

Suddenly, he drops you, and you fall to your knees, not expecting to have to support your own weight. You look back up at him and he's still pointing his gun at you, but his free hand is running over the heart-shaped container on his chest. With a hiss, it slides open, revealing his bright pink, glowing heart. He then grabs your hair, roughly, and yanks you up again, shoving your face so close to his heart you can feel the heat radiating off of it. "Lick it," he commands, and you start to brace yourself on his legs with your hands, but he knees you in the stomach for trying and growls, "Hands _off_." You'd crumple to the ground, but he still has a grip on your scalp, so you give him what he wants. 

It's hot-- almost burning. You flinch back a little the first time your tongue touches it, but you can see his cannon pointed at you out of the corner of your eye so you get back to it. The surface of his heart is smooth, like silicone, and it isn't _quite_ hot enough to burn you, at least. You chance a look upward and notice that his eyes are closed, not even bothering to watch you work. You continue to lick and suck, noting that the heart has started to drip some kind of thick, syrupy liquid that's just as hot as the rest of it. It tastes a little like honey, and a little like cherry cough syrup, but you don't exactly have time to savor it as you feel the warmth drip down your throat and chin. God. Here you were, servicing a killer robot, covered in his weird juices, and you can't help but sneak a hand down your pants to rub at yourself. You moan against him, and his eyes open. 

The grip in your hair tightens, just before he tosses you to the ground, giving you a swift kick just as you land. You cry out, and you roll over onto your hands and knees to try and stand, but he suddenly has his hand on the back of your neck pressing you into the ground and oh god, you fucked up. 

"I didn't tell you to touch yourself, you little slut." He removes his hand from your neck, only to replace it with his gun. "I show you mercy, and this is how you act? Disgusting." He rips (literally rips) your pants off of your body, leaving you naked from the waist down, and roughly grabs your ass. "Look at you. Filthy." You can't see what he's doing behind you, but you can feel it when he shoves his scalding heart against your entrance. "Is this what you want?" 

You mumble out a weak "Y-yes..." This might not be what you set out to do today, but you're sure you've never wanted anything more in your life. Suddenly, the pressure against you is gone, and you turn your head to see him putting his heart back where it belongs. You're confused, until he points his gun back in your face. 

"Too bad." You can hear a high pitched noise as his cannon arm starts to charge up, and you can stare right down the barrel as light begins to collect inside it-- until Mettaton freezes, the noise stops, and he falls to the ground, limp. 

He ran out of battery. You've never been more relieved and disappointed in your life. You sit up, lamenting the destruction of your pants, before you realize you're going to have to explain to Alphys why your pants are gone and why you're covered in pink goo. 

You consider leaving through the back door. 

**Notes for the Chapter:**

> what do you mean "NEO acts exactly like EX in canon" I can't hear you over the sound of frantically typing more terrible robot sin


	2. In which Mettaton is sorry

**Summary for the Chapter:**

> Mettaton comes to apologize for what he did the other day.

It been a few days since the... _incident_ with Mettaton, and it's basically all you've been able to think about. Sure, you almost died, but damn if it wasn't the hottest thing that had ever happened to you. Neither him nor Alphys had spoken to you since, bar one incredibly awkward conversation with the scientist where you ended up borrowing a set of pants that you're pretty sure originally belonged to Undyne. You sigh, leaning back in your chair, and resign yourself to the fact that Mettaton will probably never want anything to do with you ever again. Naturally, as soon as you're comfortable, the doorbell rings. You consider pretending you aren't home, but curiosity gets the better of you. Who would be visiting you at this hour? You open the door just enough to see, and...

Of course it's Mettaton. Why _wouldn't_ it be Mettaton?

He's in his EX form, holding a giant bouquet of mixed flowers (mostly pink, of course). He actually looks... sad? You realize you've never seen him without a smile on his face in this form. Poking his head around the flowers, he meets your gaze. "Darling, can I come in? I want to talk about what happened." Dumbstruck, you open the door fully, guiding him to your couch and watching him place the bouquet on the coffee table. You take a seat a respectable distance from him, just in case he still feels awkward about the "sex and attempted murder" thing. He's still avoiding eye contact for the most part, and has his hands folded gently in his lap.

After a long, quiet moment, he speaks, finally looking back up at you. "I'm so sorry about what happened. There's no excuse for what I tried to do to you, or... what I did do." He looks away at that, pained, and your heart aches a little.

You tell him it's okay, you know he wasn't himself at the time. He shakes his head. "I shouldn't have put you in that situation in the first place. I knew you were only trying to help me, but I still took advantage of you, and I'm sorry." Now you feel bad. But what can you say to him? _Hey, Mettaton, I actually loved it when you made me service you at gunpoint. Please do that to me again but maybe without the actual threat of murder._ He notices you lost in thought, and moves to stand up.

"Well, I've said what I needed to. I won't trouble you any more. I just hope you can forgive me--" He's cut off by you grabbing his arm, which you hadn't realized you were doing until it was too late. Well, you're in it now. You say, gently, that you weren't exactly... _unwilling,_ before. His eyes widen in surprise as he sits fully back on the couch. "Are you saying... you enjoyed that?" A gloved hand moves to his mouth, contemplating. You half-shrug, half-nod, embarrassed and a little ashamed. He leans back a little. "I had suspected, darling, but I thought that was just wishful thinking on my part..." Biting his lip, he turns his body towards you, trying to choose the right words. His eyes gleam a little as he seems to come to a decision, and _oh._ Suddenly he's straddling you, one hand stroking your cheek. 

"Let me make up for everything, sweetheart," he says, leaning in close to your face, not _quite_ touching his lips to yours, waiting for you to close the gap. Which you do, immediately, because _oh my god._ You already knew he was an amazing kisser from your brief encounters before, but this time he really means it and you can tell how much he wants you. The hand that was on your cheek has moved to the back of your head, forcing you deeper into the kiss. His other hand runs down your side before coming to rest on your hip, and you don't quite know what to do with your own hands but grabbing his ass seems like a good idea, so you do. It's softer than the hard metal you expected, almost like a rubber ball, and you can tell he can feel it when he smiles against your lips. He pulls away from your mouth, his normally perfect hair tussled just the slightest bit, and he gives you his award-winning grin as he pulls himself off you to kneel on the ground between your legs.

"Just let me take care of you," he says, running his hand up your thigh. "It's the least I can do." You nod, not trusting yourself to form words, and he reaches up to unbutton your pants.

**Notes for the Chapter:**

> CHOOSE YOUR OWN SEXVENTURE!
> 
> If you'd prefer to read a story in which the reader has a VAGINA, go to chapter THREE.
> 
> If you'd prefer to read a story in which the reader has a PENIS, go to chapter FOUR. 
> 
> They're pretty much the same besides genitals.


	3. In Which Mettaton Puts His Mouth On Your Vag

**Summary for the Chapter:**

> The sex happens.

**Notes for the Chapter:**

> This is the version of the story where the reader has a vagina.  
> If you're looking for the penis version, it's that way -->  
> No gendered pronouns etc.

He pulls them down easily, leaving you bare from the waist down except your panties (you silently thank god you chose to wear nice ones today). He gives a little _hm_ of approval as he runs his thumb along the spot where the seam meets your leg, almost making you reflexively close your legs in shame. He rests his face on the inside of your thigh (conveniently forcing you to spread your legs again), and he continues to draw lazy circles around you with his fingers everywhere but where you want it most and it's driving you crazy. Luckily, he seems to be almost as impatient as you, and he leans forward, mouthing at you gently over the fabric, and he looks up at you with hooded eyes and you swear you could have come right then.  
  
Gently, almost teasing, he finally pulls down your underwear, fully exposing you. There's no time for you to be embarrassed before he rubs his index finger on your clit, making you gasp. He runs his finger down your slit, _just barely_ dipping inside of you, and when he brings his finger up to his mouth to taste you, it's all you can do to cover your mouth before any more noises slip out of you this early in the game. He chuckles lightly before leaning in to place a kiss right on your clit, earning another gasp.  
  
It's not long before he has you breathless. He seems to know exactly how to work you over, what parts of you to hit and when, what rhythm makes you squirm in your seat, and what makes you drop your hand down from your mouth to tangle in his hair, no longer worried about things like propriety. Your other hand has a death grip on the couch, and he seems to notice, because you can feel his hand on top of yours, gently, and then without thinking, you interlace your fingers with his, and now you're holding hands with the most beautiful creature you've ever seen while he eats you out on your couch.  
  
If you died now, you'd be happy. No, wait. Something was missing.  
  
You tug gently on his hair, trying to get him to stop, and eventually manage to find the words to mumble out "M-mettaton, wait..." and he jerks back, afraid he's hurt you somehow. Still mumbling, you somehow make enough coherent words to ask him if you can do anything for him, to make him feel good. He smiles again, and this time it feels more genuine.  
  
"Darling, you don't have to do a thing for me. I'm doing this for _you_."  
  
You tell him you know, but you want to, and you swear you can see him blush. "Anything for you, sweetheart," he says, and he fiddles with something you can't see below the couch, and there's a familiar hiss before he brings up his gently beating heart. Oh. You remember that. He hands it to you gently, and you're a little afraid it's going to burn you, but this time it's simply pleasantly warm, like a cup of tea. The surface is slick with mysterious pink goop, and as you run your thumb over it, you can see him biting his lip again. You smirk just a little, and bring the heart to your mouth, letting the warm syrupy liquid fall over your tongue and down your throat. It does taste like cherries, you note right before Mettaton goes back to his business between your legs.  
  
You work up a new rhythm together. He's still using his tongue to feel you inside and out, massaging your thigh with one hand and the fingers of the other still interlaced with yours. This time, though, he's broken up occasionally by the little gasps and moans he's making when you lick and suck at his heart, rubbing and squeezing it, trying to do whatever you can for him. Soon enough, you can feel the familiar heat building at the base of your spine, and you pull him in closer to you with your heels. He seems to get the message, and keeps a steady pace on your clit, waiting for you to tip over the edge. It's not long before you do, and you swear if his head wasn't made of metal you'd have crushed it with how hard your legs clench together. As you reach your peak, you can hear him beneath you letting out a loud moan of his own, and when you come down you realize that at some point you started squeezing his heart like a stress ball and oops. You guess that was enough to make him finish, too.  
  
You slump back into the couch, exhausted and completely satisfied. He takes up a spot next to you, gingerly taking his heart back and putting it back in its chamber. You lean against him, feeling the warmth coming from his metal chest, and honestly he's not the softest pillow you've ever had but damn if you weren't comfortable. You close your eyes and sigh, perfectly content. He strokes the top of your head gently as you relax into him.  
  
"Am I forgiven, darling?"  
  
You manage to get out a _mm-hmm_ before you drift off to sleep.  
  



	4. In Which Mettaton Puts His Mouth On Your Penis

**Summary for the Chapter:**

> This is the penis version of the story.   
> If you just read chapter 3, this is the exact same thing with different genitals. 
> 
> I mean, if you want to read it again you can. I'm not stopping you.

He pulls them down easily, leaving you bare from the waist down except your underwear. He thumbs the outline of your dick through the fabric, smirking just a little at your reaction. You want to look away, but you can't take your eyes off the gorgeous robot currently leaning forward to run his tongue up your shaft, and you shudder because _my god_ that's the hottest thing you've ever seen.  
  
Luckily, he seems almost as impatient as you are, and he tugs your underwear down, freeing your dick from its cloth prison. He doesn't waste any time, taking the head of your cock into his perfect mouth, working the shaft with his hand. He pushes forward, taking your length to the hilt, and you realize that robots don't have gag reflexes.  
  
It's not long before he has you breathless. He seems to know exactly how to work you over, what makes you moan loudest, what rhythm makes you squirm in your seat, and what makes you drop your hand down from your mouth to tangle in his hair, no longer worried about things like propriety. Your other hand has a death grip on the couch, and he seems to notice, because you can feel his hand on top of yours, gently, and then without thinking, you interlace your fingers with his, and now you're holding hands with the most beautiful creature you've ever seen while he sucks your dick on your couch.  
  
If you died now, you'd be happy. No, wait. Something was missing.  
  
You tug gently on his hair, trying to get him to stop, and eventually manage to find the words to mumble out "M-mettaton, wait..." and he pulls back, afraid he's hurt you somehow. Still mumbling, you somehow make enough coherent words to ask him if you can do anything for him, to make him feel good. He smiles again, and this time it feels more genuine.  
  
"Darling, you don't have to do a thing for me. I'm doing this for _you_."  
  
You tell him you know, but you want to, and you swear you can see him blush. "Anything for you, sweetheart," he says, and he fiddles with something you can't see below the couch, and there's a familiar hiss before he brings up his gently beating heart. Oh. You remember that. He hands it to you gently, and you're a little afraid it's going to burn you, but this time it's simply pleasantly warm, like a cup of tea. The surface is slick with mysterious pink goop, and as you run your thumb over it, you can see him biting his lip again. You smirk just a little, and bring the heart to your mouth, letting the warm syrupy liquid fall over your tongue and down your throat. It does taste like cherries, you note right before Mettaton goes back to his business between your legs.  
  
You work up a new rhythm together. He's still using his that beautiful mouth of his, massaging your thigh with one hand and the fingers of the other still interlaced with yours. This time, though, he's broken up occasionally by the little gasps and moans he's making when you lick and suck at his heart, rubbing and squeezing it, trying to do whatever you can for him. Soon enough, you can feel the familiar heat building at the base of your spine, and you pull him in closer to you with your heels. He seems to get the message, and redoubles his efforts on your dick, waiting for you to tip over the edge. It's not long before you do, and you hear him sputter just a little as you cum down his throat. As you reach your peak, you can hear him beneath you letting out a loud moan of his own, and when you come down you realize that at some point you started squeezing his heart like a stress ball and oops. You guess that was enough to make him finish, too.  
  
You slump back into the couch, exhausted and completely satisfied. He takes up a spot next to you, gingerly taking his heart back and putting it back in its chamber. You lean against him, feeling the warmth coming from his metal chest, and honestly he's not the softest pillow you've ever had but damn if you weren't comfortable. You close your eyes and sigh, perfectly content. He strokes the top of your head gently as you relax into him.  
  
"Am I forgiven, darling?"  
  
You manage to get out a _mm-hmm_ before you drift off to sleep.

**Notes for the Chapter:**

> Literally every single mtt/reader fic had either a vagina or magic mystery genitals, which is fine, but I figured I'd give the penis-having individuals in the audience some love. 
> 
> Apologies for any inaccuracies. I'm not especially experienced with dicks and basically everything I know about them comes from fanfiction.


End file.
